Organic polymeric materials are subject to thermal, oxidative and ultraviolet light degradation which exhibits itself in the loss of physical properties and in the change of color. Therefore it is generally necessary to incorporate into the polymeric materials stabilizers which retard their decomposition. A variety of compounds have been employed for that purpose, the most widely used being hindered-phenolic alkanoates.
It has now been found that the polyalkylthiobenzenes of this invention are exceptionally good stabilizers against thermal and oxidative degradation. These compounds belong to a generally known class of aromatic thioethers as disclosed in Adams et al, J. Am. Chem. Soc. 81, 4927 (1959) and in U.S. Pat. Nos. 3,100,802 and 3,228,989. However the use of polyalkylthiobenzenes as stabilizers of organic substances has not been taught by the prior art. The most related class of compounds that have been used as stabilizers are polyphenyl thioethers disclosed in U.S. Pat. No. 3,647,752 and polyphenyl and polyalkyl thioethers disclosed in U.S. Pat. No. 3,751,358. Such compounds differ substantially from those of the present invention because they do not have thioalkyl groups substituted on the aromatic ring. British Pat. No. 951,933 disclose diphenylthioethers where the phenyl groups are substituted with hydroxyl and alkyl groups. The most relevant prior art might be U.S. Pat. Nos. 3,076,851 and 3,084,196 which disclose thiophenols where the benzene ring is substituted with one thioalkyl and one alkyl group. These compounds are said to be useful as antioxidant lubricating oil additives. The compounds of this invention may or may not have alkyl substituents and they carry at least two thioalkyl groups. Such compounds are substantially more efficient stabilizers, especially in crosslinked polyolefins.